Oceans face 'deadly trio' of threats, study says

11.10.2013 16:22

The world's oceans are
under greater threat than previously believed
from a "deadly trio" of global warming,
declining oxygen levels and acidification, an
international study said on Thursday.
The oceans have continued to warm, pushing
many commercial fish stocks towards the
poles and raising the risk of extinction for
some marine species, despite a slower pace
of temperature rises in the atmosphere this
century, it said.
"Risks to the ocean and the ecosystems it
supports have been significantly
underestimated," according to the
International Programme on the State of the
Ocean (IPSO), a non-governmental group of
leading scientists.
"The scale and rate of the present day
carbon perturbation, and resulting ocean
acidification, is unprecedented in Earth's
known history," according to the report,
made with the International Union for
Conservation of Nature.
The oceans are warming because of heat
from a build-up of greenhouse gases in the
atmosphere. Fertilizers and sewage that wash
into the oceans can cause blooms of algae
that reduce oxygen levels in the waters. And
carbon dioxide in the air can form a weak
acid when it reacts with sea water.
"The ‘deadly trio' of ... acidification, warming
and deoxygenation is seriously affecting how
productive and efficient the ocean is," the
study said.
Alex Rogers of Oxford University, scientific
director of IPSO, told Reuters scientists were
finding that threats to the oceans, from the
impacts of carbon to over-fishing, were
compounding one another.
"We are seeing impacts throughout the
world," he said.
EXTINCTIONS
Current conditions in the oceans were similar
to those 55 million years ago, known as the
Paleocene-Eocene thermal maximum, that led
to wide extinctions. And the current pace of
change was much faster and meant greater
stresses, Rogers said.
Acidification, for instance, threatens marine
organisms that use calcium carbonate to
build their skeletons - such as reef-forming
corals, crabs, oysters and some plankton vital
to marine food webs.
Corals might cease to grow if temperatures
rose by 2 degrees Celsius (3.6F) and start to
dissolve at 3 degrees (5.4F), the study said.
Scientists said the findings added urgency to
a plan by almost 200 governments to work
out a deal by the end of 2015 to limit a rise
in average world temperatures to less than 2
degrees Celsius (3.6F) above pre-industrial
times.
Temperatures have already risen by about 0.8
degree Celsius (1.4F). The report also urged
tougher management of fish stocks including
a ban on destructive bottom trawlers and
granting more power to local communities in
developing nations to set quotas.
Last week, a report by the U.N.'s
Intergovernmental Panel on Climate Change
(IPCC) raised the probability that mankind
was the culprit for most global warming to
95 percent, from 90 in a report in 2007.
The Global Ocean Commission, a group of
politicians working to advise governments,
urged stronger action.
"If the IPCC report was a wake-up call on
climate change, IPSO is a deafening alarm
bell on humanity's wider impacts on the
global ocean," said Trevor Manuel, co-chair
of the Commission and minister in the South
African Presidency.